1. Field of the Invention
The present invention relates to a light emitting diode luminance system, especially a light emitting diode luminance system capable of providing the short circuit protection function when LEDs thereof are damaged or breakdown.
2. Description of the Prior Art
Related art light emitting diode (LED) luminance systems usually comprise a plurality of LEDs coupled in series. When the driving voltage varies too rapidly, the LEDs or driving circuit thereof might be damaged. Please refer to FIG. 1, which shows a related art LED luminance circuit 10 comprising a plurality of LEDs 16. As shown in FIG. 1, each string of LEDs has a first end coupled to a voltage source VDC, and a second end coupled to a first end of an integrated circuit (IC) 14. The first end of the IC 14 is coupled to a first end of a current source 12. A second end of the current source 12 is coupled to the ground. When the voltage level of the voltage source VDC rises rapidly and exceeds a rated voltage, the LED luminance circuit 10 will be easily damaged or breakdown. Because the voltage level of the first end of the IC 14 is equal to the voltage level of the voltage source VDC minus the voltage level of all the functional LEDs 16 of a corresponding string of LEDs, the voltage level of the first end of the IC 14 will rise rapidly if some LEDs 16 in the string of LEDs are in breakdown. This may reduce the life span of the IC 14. And if the voltage level of the first end of the IC 14 rises to a high level exceeding a tolerance of the IC 14, the IC 14 maybe breakdown accordingly. To avoid the above issue, the IC 14 should be manufactured with high voltage process. However, in this way, the IC will be designed to have a larger area, and the cost will accordingly become higher.